Modular dart launcher with status indicator

ABSTRACT

A dart launcher launches a dart by placing the dart within a launcher bore formed within a launcher body. The launcher body also defines a central bore coupled inline with a tubing string and in fluid communication with the launcher bore. The launcher bore is formed at an angle to the central bore. A release assembly is coupled to the launcher body and includes a release rod protruding into the launcher bore to selectively release the dart. A visual indicator assembly is coupled to the launcher body downstream from the release assembly and includes a flapper protruding into the launcher bore. The release assembly is actuated by the dart rotating the flapper to rotate an arm from a non-released position to a released position.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to drop balls, plugs, or darts used tooperate well tool functions and, in particular, to a drop ball, plug, ordart launcher with a status indicator.

2. Brief Description of Related Art

Standard dart or ball launchers have a member that defines a centralbore that may be coupled inline with a drill or tubing string. Thelaunchers also include an angular bore that intersects the central boreat a shallow angle between the angular bore and the central bore. A dartor ball is dropped into the angular bore, and after opening a series ofvalves, the ball or dart is introduced into the central bore for furthermovement of the dart or ball down the borehole. There, the dart or ballwill land at a predetermined location to block the borehole and allowhydraulic tool operations. In order to minimize the potential that theball will snag or hang up as it moves from the angular bore to thecentral bore, the angle of the intersection between the two axes is asclose to zero degrees as possible. This necessitates that the launchermust be very tall to smooth out the transition between the angular boreand the central bore. The height can make the launcher very difficult toaccess and operate.

Other devices couple inline with the drill or tubing string and use aseries of valves to launch the ball or dart. The dart or ball may becomestuck or snagged at the valve openings, preventing successful release ofthe dart or drop ball. In addition, these types of devices requirebypass passages within the valves so that fluids may flow around thedarts and valves prior to launching the dart or ball. These passagesrestrict fluid flow through the running string and may become clogged.Clogging of these passages will, in turn, require stoppage of drillingoperations in order to remove and reset the launcher for operation. Evenwhen not blocked, these passages may restrict the flow of fluiddownhole, causing further complications in drilling operations.

Still other devices may couple inline with the drill or tubing stringand use a series of balls to launch darts or plugs contained within thedevice. These devices rely on complex landing and sliding sleevedevices, to bypass the fluids around the landed balls and darts, againrestricting fluid flow through the string. These devices also do notprovide an indication that the proper dart or plug has been launchedfollowing landing of the ball.

Generally, following launch of a ball, dart, or plug, operators wait foran increase in pressure within the tubing string to indicate that theball, dart, or plug has properly released into the drill string andlanded at the ball, dart, or plug seat. Operators may then proceed withoperations such as cementing or running tool actuation. However, in somewells, particularly in deep subsea wells, the distances between theoperating platform and the landing location are large enough that it maytake over an hour for the dart to land at the seat. As a result,operators may proceed with operations following release of the ball,dart, or plug but before they have received any indication that theball, dart, or plug has landed. In the event that the ball, dart, orplug becomes hung up or snagged in the launcher and does not releaseinto the tubing string, the well may be significantly damaged,necessitating expensive and time consuming repair operations. Somelaunchers include an electrical system for indicating that the dart,ball, or plug has released, however these systems require complexcomponents that are prone to failure and difficult to adapt to changingtypes and sizes of balls, darts, and plugs. Thus, there is a need for alauncher that launches the dart or ball from an inline coupling withoutrestricting fluid flow through the central bore of the tubing and thatmay provide an indication of a successful launch of the ball, dart, orplug.

SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, andtechnical advantages are generally achieved, by preferred embodiments ofthe present invention that provide a modular dart launcher with a statusindicator and a method for using the same.

In accordance with an embodiment of the present invention, a wellboredrop member launcher is disclosed. The launcher includes a launcher bodydefining a central bore having a central bore axis, the launcher bodyhaving a lower end configured to attach to a string of pipe extendinginto a wellbore. The launcher body also defines a launcher bore having alauncher bore axis at an angle to the central bore axis, the launcherbore in fluid communication with the central bore. A release assembly iscoupled to the launcher body and has a release rod protruding into thelauncher bore to prevent movement of a drop member positioned within thelauncher bore in a drop member hold position. The release assembly isconfigured to move the release rod to a drop member release position toselectively release the drop member positioned within the launcher bore.A visual indicator assembly is, coupled to the launcher body and isconfigured to provide a mechanically produced visual indication that thedrop member has moved from the launcher bore to the central bore.

In accordance with another embodiment of the present invention, awellbore drop member launcher is disclosed. The launcher includes alauncher body defining a central bore having a central bore axis, thelauncher body having a lower end configured to attach to a tubing stringextending into a wellbore. The launcher body also defines a launcherbore having a launcher bore axis at an angle to the central bore axis.The launcher bore is in fluid communication with the central bore. Arelease assembly is coupled to the launcher body and has a release rodprotruding into the launcher bore to prevent movement of a drop memberpositioned within the launcher bore into the tubing string. The releaseassembly is configured to move the release rod with a piston assemblyfrom a drop member hold position to a drop member release position toselectively release the drop member. The piston assembly also biases therelease rod to the drop member hold position. A pressure passage isdefined by the release rod and is configured to equalize pressurebetween a compressible portion of the piston assembly and the launcherbody, preventing premature drop member release. The pressure passageextends from an end of the release rod disposed within the launcher borethrough a center of the release rod to an annular chamber within thepiston assembly. An indicator housing is coupled to the launcher bodyproximate to an indicator bore that is defined by the launcher body andextends from an exterior of the launcher body to the launcher bore. Anindicator rod extends through the indicator housing into the indicatorbore. The indicator rod has a flapper formed near an end of theindicator rod and an arm secured to an opposite end of the indicatorrod. The flapper and the arm are perpendicular to the indicator rod andparallel to each other. The flapper extends from the indicator bore intothe launcher bore and the arm is visible to an operator. As the dropmember passes the flapper it will rotate the flapper, indicator rod, andarm to indicate release of the drop member.

In accordance with yet another embodiment of the present invention, amethod for launching a drop member into a wellbore tubing string isdisclosed. The method provides a launcher body having a central borewith a central bore axis and a launcher bore with a launcher bore axisat an angle to the central bore axis and in fluid communication with thecentral bore. The method places a drop member in the launcher bore andresting the drop member on a release rod of a release assembly coupledto the launcher body. The method couples a visual indicator assembly tothe launcher body so that the visual indicator assembly is incommunication with the launcher bore at a location downstream from therelease assembly. The method couples the launcher body in line with thetubing string so that the central bore of the launcher body aligns witha body passage through the tubing string. The method then actuates therelease assembly to allow the drop member to flow from the launcher bodyinto the central bore where the drop member may move down the tubingstring. The method actuates the visual indicator assembly with the dropmember as the drop member moves from the launcher bore into the centralbore.

An advantage of a preferred embodiment is that it provides a dartlauncher that may be used in high fluid pressures situations. Inaddition, the disclosed embodiments provide an apparatus and method toeasily launch a ball, dart, or plug with minimal human intervention.Still further, the disclosed embodiments provide a modular apparatusthat allows for variation in the size of the ball, dart, or pluglaunched. Sill further, the disclosed embodiment provides a visualindicator for an operator to confirm the successful launch of the ball,dart, or plug that does not rely on complicated electronics systems thatmay be prone to failure in harsh operating environments.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features, advantages and objects of theinvention, as well as others which will become apparent, are attained,and can be understood in more detail, more particular description of theinvention briefly summarized above may be had by reference to theembodiments thereof which are illustrated in the appended drawings thatform a part of this specification. It is to be noted, however, that thedrawings illustrate only a preferred embodiment of the invention and aretherefore not to be considered limiting of its scope as the inventionmay admit to other equally effective embodiments.

FIG. 1 is a perspective view of a dart launcher in accordance with anembodiment of the present invention.

FIG. 2 is a sectional view of the dart launcher taken along ling 2-2 ofFIG. 1.

FIG. 3 is a sectional view of a release assembly of the dart launchertaken along line 3-3 of FIG. 1.

FIG. 4 is an enlarged view of a portion of the dart launcher indicatedat FIG. 2.

FIG. 4A is an enlarged view of a surface of the release assembly takenalong line 4A of FIG. 3.

FIG. 5 is an enlarged view of the portion of the dart launcher indicatedat FIG. 2 following release of a dart.

FIG. 5A is an enlarged view of the surface of the release assembly takenalong line 5A of FIG. 5.

FIG. 6 is a perspective view of a visual indicator assembly of the dartlauncher.

FIG. 6A is a front view of the visual indicator assembly of FIG. 6.

FIG. 7 is a sectional view of the visual indicator assembly taken alongline 7-7 of FIG. 2.

FIG. 8 is a sectional view of a portion of a spring plunger of thevisual indicator assembly in pre-release position taken along line 8-8of FIG. 6.

FIG. 9 is a perspective view of the visual indicator assembly followingrelease of the dart.

FIG. 9A is a front view of the visual indicator assembly of FIG. 9.

FIG. 9B is a sectional view of a portion of a spring plunger of thevisual indicator assembly in a post-release position taken along line9B-9B of FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be described more fully hereinafter withreference to the accompanying drawings which illustrate embodiments ofthe invention. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theillustrated embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Like numbers refer to like elements throughout, and the prime notation,if used, indicates similar elements in alternative embodiments orpositions.

In the following discussion, numerous specific details are set forth toprovide a thorough understanding of the present invention. However, itwill be obvious to those skilled in the art that the present inventionmay be practiced without such specific details. Additionally, for themost part, details concerning drilling rig operation, well toolmanufacture, well tool operation, well tool uses, and the like have beenomitted inasmuch as such details are not considered necessary to obtaina complete understanding of the present invention, and are considered tobe within the skills of persons skilled in the relevant art.

Referring to FIG. 1, a dart launcher 11 is shown. Dart launcher 11includes an upper tubular member or top pup 13 adapted to connect to atubular member of a tubing or drill string. Fluid, such as drillingfluid, may circulate through dart launcher 11 from an external sourcecoupled to top pup 13. Dart launcher 11 also includes a lower tubularmember or bottom pup 15 adapted to connect to a tubular member of atubing or drill string. The tubing string may continue into a well totransport the fluid to a. subsurface location. A person skilled in theart will recognize that top pup 13 and bottom pup 15 have ends adaptedto connect dart launcher 11 in line in a tubing string. In theillustrated embodiment, the ends of top pup 13 and bottom pup 15comprise threaded connectors. In other exemplary embodiments, the endsof top pup 13 and bottom pup 15 may be any suitable connector type suchthat dart launcher 11 may couple inline to a tubing string.

Dart launcher 11 also includes a launcher body 17, a dart releaseassembly 19, and a visual indicator assembly 21. Top pup 13 and bottompup 15 may secure to or couple to launcher body 17 on opposite ends oflauncher body 17 so that top pup 13 and bottom pup 15 are coaxial withan axis 23 of a central bore 25 of launcher body 17 (FIG. 2). In anexemplary embodiment, top pup 13 and bottom pup 15 secure to launcherbody 17 through threaded connections. A person skilled in the art willunderstand that other connection types may be used.

Referring to FIG. 2, a sectional view of launcher body 17 is shown.Launcher body 17 defines central bore 25 and a launcher bore 27 thatintersects central bore 25, allowing for fluid communication betweencentral bore 25 and launcher bore 27. Launcher bore 27 intersectscentral bore 25 at opening 35. Opening 35 will be of a size and shape toallow a ball, plug, or dart 33 to pass from launcher bore 27 intocentral bore 25. Launcher bore 27 has an axis 29. Axis 29 my intersectaxis 23 at an angle 31. Angle 31 may comprise any suitable angle suchthat a drop member or dart 33 may pass from launcher bore 27 intocentral bore 25 for travel through a coupled tubing string. In theillustrated embodiment, central bore 25 and launcher bore 27 are formedfrom a single launcher body 17. In other exemplary embodiments, centralbore 25 and launcher bore 27 may be defined by separate bodies coupledor secured together. Dart release assembly 19 couples to launcher body17 proximate to launcher bore 27 such that dart release assembly 19 mayselectively allow passage of dart 33 from launcher bore 27 into centralbore 25 through opening 35. Visual indicator assembly 21 will couple orsecure to launcher body 17 proximate to opening 35 such that as dart 33passes from launcher bore 27 into central bore 25, described in moredetail below, visual indicator assembly 21 will indicate such passage.For illustrative purposes, visual indicator assembly 21 has been shownin the sectional view of FIG. 2 to aid in the illustration of therelationship between visual indicator assembly 21 and dart releaseassembly 19.

Referring to FIG. 3, a side sectional view of dart release assembly 19is shown. Dart release assembly 19 includes a release housing 37 and apressure chamber 39. Pressure chamber 39 may be a hydraulic pressurechamber, pneumatic pressure chamber, or the like. Pressure chamber 39 iscoupled to an end of release housing 37 by any suitable means. In anexemplary embodiment, pressure chamber 39 is bolted to release housing37. Pressure chamber 39 includes a piston 41 extending from an interiorof pressure chamber 39 into an actuator bore 43 of release housing 37.Piston 41 has a piston head 45 that seals to the interior surfaces ofpressure chamber 39 to divide pressure chamber 39 into two sections.Each section of pressure chamber 39 is in communication with a pressuresource through ports 47, 49. The pressure source may be a hydraulicpressure source that supplies hydraulic pressure through ports 47, 49.In other embodiments, the pressure source may be a pneumatic pressuresource that supplies pneumatic pressure through ports 47, 49. In theexemplary embodiment, port 47 comprises a dart release port, and port 49comprises a vent. Pressure may be supplied to port 47 to assert a forceon piston head 45 to move piston 41 from a dart hold position, wheredart 33 (FIG. 2) is prevented from moving into central bore 25, to adart release position, where dart 33 (FIG. 5) is allowed to move intocentral bore 25. Pressure within pressure chamber 39 will vent throughport 49 when pressure is supplied through port 47 to move piston 41 fromthe dart hold to the dart release position. In other embodiments,pressure may be supplied to port 49 to assert a force on piston head 45to move piston 41 from the dart release position to the dart holdposition, shown in FIG. 3.

A shaft of piston 41 passes through a spring 51 disposed within actuatorbore 43. An end of the shaft of piston 41 will couple to a spring perch53 disposed within actuator bore 43 opposite pressure chamber 39 in thedart hold position. Spring perch 53 may move through actuator bore 43with piston 41 in response to application of pressure to pressurechamber 39. Spring 51 will be positioned to bias spring perch 51 to thedart hold position of FIG. 3. Actuator bore 43 will include an indicatorwindow 55 extending a portion of a length of actuator bore 43. Anindicator screw 57 will pass through indicator window 55 and couple tospring perch 53 such that a head of indicator screw 57 will remaindisposed within indicator window 55. As spring perch 53 moves throughactuator bore 43 indicator screw 57 will move from an end of window 55to an opposite end of window 55. In an exemplary embodiment, indicatorscrew moves from an area spaced from pressure chamber 39 to an areaproximate to pressure chamber 39.

Release housing 37 defines actuator bore 43 and a rod bore 59. Rod bore59 and actuator bore 43 are separated by a chamber wall 61 having a portfor communication between actuator bore 43 and rod bore 59. Spring perch53 may include a protrusion extending into the port of chamber wall 61such that a release rod 63 may couple to spring perch 53. As shown inFIG. 4, a seal 60 may be positioned within chamber wall 61 to seal torelease rod 63. Referring to FIG. 3, a surface of spring perch 53 maycontact chamber wall 61 in the dart hold position, limiting movement ofspring perch 53 away from pressure chamber 39. Release rod 63 extendsfrom rod bore 59 to an exterior of release housing 37. Release rod 63couples to spring perch 53 such that as spring perch 53 moves withpiston 61, release rod 63 will move in response. Release rod 63 includesa flange portion 65 that seals with a seal 66 (FIG. 4) to rod bore 59.Flange portion 65 may be spaced from an end of release rod 63 coupled tospring perch 53 to define an annular passage 69 between flange portion65 and chamber wall 61 in the dart hold position of FIGS. 3 and 4.Release rod 63 will include a pressure passage 67 extending through alength of release rod 63 and in fluid communication with annular passage69. Launcher bore 27 will be in fluid communication with annular passage69 through pressure passage 67 such that a hydraulic pressure oflauncher bore 27 will be substantially equivalent to the hydraulicpressure within annular passage 69. Release housing 37 further includesa flange 71 formed on an end of release housing 37 opposite pressurechamber 39. Flange 71 provides a mating contact to couple dart releaseassembly 19 to launcher body 17. In the illustrated embodiment, flange71 is bolted to launcher body 17.

Referring to FIG. 4, dart release assembly 19 is shown coupled tolauncher body 17 and in the dart hold position of FIG. 3. As shown, anend of release rod 63 will extend from an end of releasing housing 37and pass through a release rod bore 73 formed in a wall of launcher body17. Release rod 63 will seal to release rod bore 73 with a seal 74positioned within release rod bore 73. Release rod 63 will extend asufficient distance into launcher bore 27 to prevent passage of dart 33from launcher bore 27 into central bore 25. A person skilled in the artwill recognize that release rod 63 extends into launcher bore 27 asufficient length to allow for variation in the size of dart 33. Thus,dart launcher 11 may be used in various types of operations to releaseor launch multiple types of darts 33.

As shown in FIG. 4A, indicator screw 57 will be positioned in an end ofwindow 55 proximate to launcher body 17. Referring to FIG. 5, pressurehas been supplied to port 47, causing piston 41 to move to the dartrelease position. In response, spring perch 53 has moved toward pressurechamber 39, compressing spring 51. Release rod 63 will be pulled intorod bore 59 until flange portion 65 contacts chamber wall 61 oppositeactuator bore 43. This will pull release rod 63 completely from launcherbore 27, allowing dart 33 to move freely from launcher bore 27 intocentral bore 25 for further movement through a tubing string coupled tobottom pup 15 (FIG. 1). As shown in FIG. 5A, when spring perch 53 movesfrom the dart hold position to the dart release position, indicatorscrew 57 will move through indicator window 55 from a position proximateto launcher body 17 (FIG. 4A) to a position proximate to pressurechamber 39 (FIG. 5A).

Referring to FIG. 6, visual indicator assembly 21 is shown. Visualindicator assembly 21 includes an indicator housing 75, and an indicatorrod 77. Indicator rod 77 has an interior end 76 and an exterior end 78.Indicator rod 77 will pass through an indicator housing bore 79 (FIG. 7)extending through indicator housing 75. Indicator housing 75 will definea flange 81 adapted to secure visual indicator assembly 21 to launcherbody 17. In the illustrated embodiment, flange 81 defines a plurality ofbores through which a plurality of bolts are passed to thread intocorresponding threaded bores of launcher body 17. A flapper 83 is formednear interior end 76 of indicator rod 77. Flapper 83 will be orthogonalto indicator rod 77. Indicator rod 77 will have a length greater than alength of indicator housing 75 such that, when indicator rod 77 ispassed through indicator housing 75, interior end 76 having flapper 83will protrude from indicator housing 75 into launcher body 17 as shownin FIG. 7. Exterior end 78 of indicator rod 77 will protrude from anopposite side of indicator housing 75. An arm 85 will be secured toindicator rod 77 on exterior end 78. In the illustrated embodiment, arm85 is orthogonal to indicator rod 77 and extends from indicator rod 77parallel to flapper 83.

Referring to FIG. 7, indicator rod 77 also includes an indicator flange87 formed between interior end 76 and exterior end 78. Indicator flange87 will define an outward facing shoulder 89 adapted to contact aninwardly facing shoulder 91 formed on an interior end of indicatorhousing 75. Contact between outward facing shoulder 89 and inwardlyfacing shoulder 91 will limit movement of indicator rod 77 in an outwarddirection. A seal 90 will be positioned in indicator housing bore 79 toseal indicator rod 77 to indicator housing bore 79 between outwardfacing shoulder 89 of indicator flange 87 and exterior end 78 ofindicator rod 77.

Indicator housing 75 will secure to launcher body 17 so that indicatorrod 77 will extend into an indicator bore 93. A seal 94 will bepositioned within indicator housing 75 to seal an outer diameter ofindicator housing 75 to indicator bore 93. Indicator bore 93 extendsfrom an exterior surface of launcher body 17 to launcher bore 27. Akeyhole 95 may be formed in an interior end of indicator bore 93.Interior end 76 of indicator rod 77 inserts into keyhole 95 so thatindicator rod 77 may rotate on an axis 97. Flapper 83 will be spacedalong axis 97 from interior end 76 so that interior end 76 may fullyseat within keyhole 95. When indicator rod 77 is positioned withinindicator bore 93 and seated within keyhole 95, flapper 83 will extendinto launcher bore 27. In the illustrated embodiment, flapper 83 willextend from indicator rod 77 such that axis 29 of launcher bore 27 maypass through an outer end of flapper 83. In other embodiments, the outerend of flapper 83 may be proximate to axis 29 of launcher bore 27, butaxis 29 may not pass through the outer end of flapper 83.

As shown in FIG. 6, visual indicator assembly 21 also includes a springplunger 99 positioned within a spring plunger bore 101 formed inindicator housing 75. Referring to FIG. 8, spring plunger bore 101extends from an exterior of indicator housing 75 to indicator housingbore 79. Spring plunger 99 will be disposed within spring plunger bore101. Spring plunger 99 includes a plunger housing 103, a plunger 105,and a spring member 107. Plunger housing 103 secures within springplunger bore 101 against a downward facing shoulder 109. Plunger housing103 has an open end proximate to indicator housing bore 79 into whichplunger 105 inserts. Spring member 107 will be disposed between aninternal shoulder 111 of indicator housing 103 and an end 113 of plunger105 proximate to an exterior of indicator housing 75. Plunger 105includes an end 115 opposite end 113 and proximate to indicator housingbore 79. Plunger 105 includes a flange 117 between end 113 and exteriorend 115. Flange 117 defines a shoulder 119 facing indicator housing bore79. Exterior end 115 protrudes from flange 117 toward indicator housingbore 79. During operation of visual indicator assembly 21, spring member107 will bias plunger 105 to the position illustrated in FIG. 8, whereshoulder 119 will contact an oppositely facing shoulder 121 to limitmovement of plunger 105. As shown, exterior end 115 may seat within apre-launch detent 123 formed on an exterior surface of indicator rod 77.When exterior end 115 seats within pre-launch detent 123 rotation ofindicator rod 77 will be stopped. When not in the position shown in FIG.8, exterior end 115 may be in contact with an exterior surface ofindicator rod 77, but shoulder 119 will be spaced from oppositely facingshoulder 121, allowing for exterior end 115 to move into pre-launchdetent 123 when indicator rod 77 is rotated.

As shown in FIG. 9B, indicator rod 77 includes a post-launch detent123′. Pre-launch detent 123 will be circumferentially spaced frompost-launch detent 123′. When flapper 83 extends into launcher bore 27as shown in FIGS. 2, 6, and 7, exterior end 115 of plunger 105 willextend into pre-launch detent 123 as shown in FIG. 8. In this manner,spring plunger 99 will prevent rotation of indicator rod 77 prior tolaunch of dart 33 so that visual indicator assembly 21 will notincorrectly indicate a launch of dart 33. When dart 33 is launched, dart33 will overcome the spring force of spring member 107, allowing forrotation of indicator rod 77 and moving flapper 83 to the position ofFIG. 9. Exterior end 115 of plunger 105 will then extend intopost-launch detent 123′ (FIG. 9B), which is circumferentially spacedfrom pre-launch detent 123, to prevent additional rotation of indicatorrod 77.

During operation of dart launcher 11, dart release assembly 19 will bein the position shown in FIGS. 2, 3, 4, and 4A; visual indicatorassembly 21 will be in the position illustrated in FIGS. 2, 6, 6A, and7. Referring to FIG. 2, dart 33 will be placed into launcher bore 27 andan end of dart 33 will rest on release rod 63 (FIG. 4). As shown in FIG.2, a plug 125 will be placed within launcher bore 27 behind dart 33 tolimit entry of undesired objects into launcher bore 27 and preventrelease of fluid from launcher bore 27. As shown in FIGS. 2, 6, 6A, and7, flapper 83 will extend into launcher bore 27 perpendicular to axis 29of launcher bore 27 so that a flat portion of flapper 83 may contact anobject moving through launcher bore 27. Similarly, arm 85 will beperpendicular to launcher bore 27. Pressure passage 67 will equalizepressure between annular passage 69 and launcher bore 27 to preventhydraulic pressure in launcher bore 27 from acting on release rod 63 tocause premature release. Plunger 115 of FIG. 8 will be positioned withinpre-launch detent 123.

When release of dart 33 is desired, pressure will be supplied to port 47to act on piston head 45. This will result in movement of piston 41 fromthe position shown in FIG. 3 to a position where piston head 45 isproximate to port 49. As shown in FIG. 5, this will result in movementof release rod 63 from launcher bore 27 to allow dart 33 to move fromlauncher bore 27 into central bore 25. Indicator screw 57 will move fromthe position proximate to launcher body 17 as shown in FIG. 4A to theposition spaced further from launcher body 17 as shown in FIG. 5A.

As dart 33 moves through launcher bore 27, it will contact flapper 83 asshown in FIG. 7. Flapper 83 will minimally resist movement of dart 33;thus, dart 33 will cause flapper 83, and consequently indicator rod 77to rotate as dart 33 moves past visual indicator assembly 21. Asindicator rod 77 rotates, plunger 105 will release from pre-launchdetent 123 and bring post-launch detent 123′ proximate to plunger 105,allowing exterior end 115 of plunger 105 to move into post-launch detent123′ as shown in FIG. 9B. This will arrest rotation of indicator rod 77in the position shown in FIGS. 9 and 9A. As shown, arm 85 will undergo aninety degree rotation so that arm 83 will be generally parallel tolauncher bore 27 as shown in FIG. 5. This ninety degree rotation willindicate to an operator that dart 33 has successfully moved fromlauncher bore 27 into central bore 25 for further movement down acoupled drill string.

Accordingly, the disclosed embodiments provide numerous advantages. Forexample, the disclosed embodiments provide a dart launcher capable oflaunching darts, balls, or plugs of different sizes. In addition, thedisclosed embodiments provide a pressure balancing system to preventpremature release of the dart that may be caused by hydraulic pressurewithin the launcher bore. The disclosed embodiments also allow formaintenance of circulation pressure within the coupled tubing stringwhile dropping the dart. Still further, the disclosed embodimentsprovide a visual indicator of a successful dart launch, that requires noexternal energy source, can be seen from a distance, and is easy toassemble.

It is understood that the present invention may take many forms andembodiments. Accordingly, several variations may be made in theforegoing without departing from the spirit or scope of the invention.Having thus described the present invention by reference to certain ofits preferred embodiments, it is noted that the embodiments disclosedare illustrative rather than limiting in nature and that a wide range ofvariations, modifications, changes, and substitutions are contemplatedin the foregoing disclosure and, in some instances, some features of thepresent invention may be employed without a corresponding use of theother features. Many such variations and modifications may be consideredobvious and desirable by those skilled in the art based upon a review ofthe foregoing description of preferred embodiments. Accordingly, it isappropriate that the appended claims be construed broadly and in amanner consistent with the scope of the invention.

What is claimed is:
 1. A wellbore drop member launcher comprising: alauncher body defining a central bore having a central bore axis, thelauncher body having a lower end configured to attach to a string ofpipe extending into a wellbore; the launcher body defining a launcherbore having a launcher bore axis at an angle to the central bore axis,the launcher bore in fluid communication with the central bore; arelease assembly coupled to the launcher body and having a release rodprotruding into the launcher bore to prevent movement of a drop memberpositioned within the launcher bore in a drop member hold position;wherein the release assembly is configured to move the release rod to adrop member release position to selectively release the drop memberpositioned within the launcher bore; and a visual indicator assemblycoupled to the launcher body and configured to provide a mechanicallyproduced visual indication that the drop member has moved from thelauncher bore to the central bore.
 2. The wellbore drop member launcherof claim 1, wherein the release assembly comprises: a piston assemblycoupled to the release rod and configured to move the release rodbetween the drop member hold position and the drop member releaseposition; and wherein the piston assembly biases the release rod to thedrop member hold position.
 3. The wellbore drop member launcher of claim2, further comprising: a release body housing interposed between thepiston assembly and the launcher body, the release rod at leastpartially disposed within the release body housing when in the dropmember hold position and a portion of the piston assembly coupling tothe release rod within the release body housing; a window having alength formed in a portion of a release body housing; an indicator screwthreaded into the portion of the piston assembly so that an end of thescrew is visible through the window; and wherein the indicator screwmoves from a first end of the window to a second end of the window whenthe piston assembly operates to move the release rod between the dropmember hold and the drop member release positions, providing a visualindication of release assembly actuation.
 4. The wellbore drop memberlauncher of claim 3, wherein: the release rod defines a pressure passageextending from an end of the release rod disposed within the launcherbore through a center of the release rod to an annular chamber withinthe release body housing; and wherein the pressure passage is configuredto equalize pressure between the release body housing and the launcherbore to prevent premature dart member release.
 5. The wellbore dropmember launcher of claim 2, wherein the piston assembly is ahydraulically actuated piston assembly.
 6. The wellbore drop memberlauncher of claim 2, wherein the piston assembly is a pneumaticallyactuated piston assembly.
 7. The wellbore drop member launcher of claim1, wherein the visual indicator assembly comprises: an indicator boredefined by the launcher body extending from an exterior of the launcherbody to the launcher bore; an indicator housing coupled to the launcherbody proximate to the indicator bore; an indicator rod extending throughthe indicator housing into the indicator bore; a flapper on an endportion of the indicator rod; wherein the flapper is perpendicular tothe indicator rod and extends from the indicator bore into the launcherbore; an arm secured to an end of the indicator rod that protrudes fromthe indicator housing and located so as to be visible to an operator;wherein the arm extends from the indicator rod perpendicular to theindicator rod and parallel to the flapper; and wherein as the dropmember passes the flapper it rotates the flapper, indicator rod, and armto indicate release of the drop member.
 8. The wellbore drop memberlauncher of claim 7, further comprising: a pre-release detent formed ina surface of the indicator rod; a post-release detent formed in asurface of the indicator rod axially aligned with the pre-release detentand circumferentially spaced from the pre-release detent; and a springplunger disposed within the indicator housing and adapted to insert intothe pre-release detent to limit rotation of the indicator rod prior topassage of the drop member; and the spring plunger further adapted torelease from the pre-release detent to allow rotation of the indicator,rod as the drop member passes and insert into the post-release detent toprevent further rotation of the indicator rod following passage of thedrop member.
 9. The wellbore drop member launcher of claim 7, whereinthe flapper, indicator rod, and arm rotate ninety degrees.
 10. Awellbore drop member launcher comprising: a launcher body defining acentral bore having a central bore axis, the launcher body having alower end configured to attach to a tubing string extending into awellbore; the launcher body defining a launcher bore having a launcherbore axis at an angle to the central bore axis, the launcher bore influid communication with the central bore; a release assembly coupled tothe launcher body and having a release rod protruding into the launcherbore to prevent movement of a drop member positioned within the launcherbore into the tubing string; wherein the release assembly is configuredto move the release rod with a piston assembly from a drop member holdposition to a drop member release position to selectively release thedrop member; wherein the piston assembly biases the release rod to thedrop member hold position; a pressure passage defined by the release rodand configured to equalize pressure between a compressible portion ofthe piston assembly and the launcher body to prevent premature dropmember release, the pressure passage extending from an end of therelease rod disposed within the launcher bore through a center of therelease rod to an annular chamber within the piston assembly; anindicator housing coupled to the launcher body proximate to an indicatorbore defined by the launcher body and extending from an exterior of thelauncher body to the launcher bore; an indicator rod extending throughthe indicator housing into the indicator bore, the indicator rod havinga flapper on an end portion of the indicator rod and an arm secured toan opposite end of the indicator rod; wherein the flapper and the armare perpendicular to the indicator rod and parallel to each other;wherein the flapper extends from the indicator bore into the launcherbore and the arm is located so as to be visible to an operator; whereinas the drop member passes the flapper it will rotate the flapper,indicator rod, and arm to indicate release of the drop member.
 11. Thewellbore drop member launcher of claim 10, further comprising: a releasebody housing coupling the piston assembly to the launcher bore, therelease rod partially disposed within the release body housing; a windowhaving a length formed in a portion of a release body housing; anindicator screw threaded into a portion of the piston assembly so thatan end of the screw is visible through the window; and wherein theindicator screw moves from a first end of the window to a second end ofthe window when the piston assembly operates to move the release rod,providing a visual indication of release assembly actuation.
 12. Thewellbore drop member launcher of claim 10, wherein the piston assemblyis a hydraulically actuated piston assembly.
 13. The wellbore dropmember launcher of claim 10, wherein the piston assembly is apneumatically actuated piston assembly.
 14. The wellbore drop memberlauncher of claim 10, further comprising: a pre-release detent formed ina surface of the indicator rod; a post-release detent formed in asurface of the indicator rod axially aligned with the pre-release detentand circumferentially spaced from the pre-release detent; and a springplunger disposed within the indicator housing and adapted to insert intothe pre-release detent to limit rotation of the indicator rod prior topassage of the drop member; and the spring plunger further adapted torelease from the pre-release detent to allow rotation of the indicatorrod as the drop member passes and insert into the post release detent toprevent further rotation of the indicator rod following passage of thedrop member.
 15. The wellbore drop member launcher of claim 10, whereinthe flapper, indicator rod, and arm rotate ninety degrees.
 16. A methodfor launching a drop member into a wellbore tubing string, comprising:(a) providing a launcher body having a central bore with a central boreaxis and a launcher bore with a launcher bore axis at an angle to thecentral bore axis and in fluid communication with the central bore; (b)placing a drop member in the launcher bore and resting the drop memberon a release rod of a release assembly coupled to the launcher body; (c)coupling a visual indicator assembly to the launcher body so that thevisual indicator assembly is in communication with the launcher bore ata location downstream from the release assembly; (d) coupling thelauncher body in line with the tubing string so that the central bore ofthe launcher body aligns with a body passage through the tubing string;(e) actuating the release assembly to allow the drop member to move fromthe launcher body into the central bore where the drop member may movedown the tubing string; and (f) actuating the visual indicator assemblywith the drop member as the drop member moves from the launcher boreinto the central bore.
 17. The method of claim 16, wherein step (e)comprises applying hydraulic pressure to a piston assembly of therelease assembly to move the release rod from the launcher bore.
 18. Themethod of claim 16, wherein step (e) comprises applying pneumaticpressure to a piston assembly of the release assembly to move therelease rod from the launcher bore.
 19. The method of claim 16, whereinstep (f) comprises: moving a flapper of the visual indicator assemblywith the drop member to rotate an indicator rod and an arm coupled tothe indicator rod; and signaling to an operator that the drop member hasmoved into the central bore with rotation of the arm.
 20. The method ofclaim 19, wherein further comprising: securing a spring plunger within ahousing of the visual indicator assembly adapted to insert into a pairof circumferentially spaced detents; and limiting rotation of theindicator rod by inserting a plunger of the spring plunger into thedetents.